Continuous nondestructive monitoring of larval feeding activity and development of the bamboo powderpost beetle Dinoderus minutus using acoustic emission

Abstract

The life history and feeding biology of the bamboo powderpost beetle Dinoderus minutus remain poorly understood because the beetles’ oviposition, development, and feeding take place inside bamboo culms. In this study, acoustic emission (AE) monitoring was applied for continuous nondestructive analysis of larval feeding activity and development from the first instar to adult eclosion. Newly hatched larvae were inoculated individually into pieces of madake (Phyllostachys bambusoides) culms. AE hits were recorded using single AE sensors fixed onto the bamboo pieces. Generation of AE hits indicated that larval feeding activity had begun after inoculation. Based on the time course of the hourly AE hit rate, the larvae were feeding constantly during each instar, and feeding activity only ceased during periods of ecdysis and pupation. Half of the individuals examined underwent seven instars and the other half underwent eight instars. The time course of AE hit rate per 5 min exhibited periodic cycles, where continuous meals were separated by inactive phases of ca. 5 min, with an average dominant period of each instar ranging between 0.76 and 2.19 h. After correcting the AE data based on distance attenuation of AE waves, the tendency that AE amplitude increased as the larvae developed through ecdysis events became more apparent. AE monitoring continued after adult eclosion, and the feeding activity of the newly emerged adults continued almost ceaselessly during the Reifungsfrass period.